Acrylic latex sealants are characterized by many desirable properties including high strength, high Shore A hardness, good flexibility and good dry adhesion to many substrates. However, they have one major weakness--poor wet adhesion. If the acrylic latex sealant is immersed in water for continuous periods of time, i.e. 24 hours or longer, total loss of adhesion can occur.
Water resistant acrylic latex sealants have been described by Bullman, in U.S. Pat. No 4,340,524, Chang, in U.S. Pat. No. 4,626,567, Roos, in U.S. Pat. No. 3,758,306, and Benjamin, in U.S. Pat. No. 4,486,565, in which acrylic latex resins are blended with aqueous emulsions of hydrolyzed organosilanes such as gamma-aminopropyltrimethoxysilane at levels of 0.1 to 1.0% by weight silane. Chang, in U.S. Pat. No. 4,626,567, also discloses use of 0.5% fumed silica as a hydrophobic agent in an acrylic latex caulk.
Thomas, in U.S. Pat. No. 3,575,910, describes silicone-acrylate copolymer aqueous emulsions for coatings with improved weatherability. Other silicone-acrylate polymer compositions characterized by improved moisture resistance are disclosed by Wheeler, in U.S. Pat. No. 3,836,598, Hattori, in U.S. Pat. No. 4,478,990, Riek, et al., in U.S. Pat. Nos. 4,491,650 and 4,567,107, and Kama Kuho, in U.S. Pat. No. 4,496,611.
Stockman, in U.S. Pat. No. 3,699,067, discloses use of low levels of trimethylsilyl stopped polydimethylsiloxane oil used to plasticize an acrylic terpolymer. The acrylic terpolymer with siloxane oil is dissolved in ethanol (25% solids solution) and used as a protective coating with antiadhesion, i.e. "release", characteristics.
The object of this invention is to provide acrylic latex based sealent compositions which will withstand immersion in water for prolonged periods without loss of adhesion. It is another object of the present invention to modify acrylic latex based sealant by addition of a polysiloxane to improve properties. Still further objects of the invention will become apparent from the following description.